Symptoms of a dead 50A relay in 85.5

[Damo]

This may help someone as it had me stumped for many hours over the weekend.

I discovered that the wipers/washer didn't work and also the fan blower wasn't working. Looong story short (which eventually involved removing & dismantling the fuse board to see how it all connected) I discovered the 50A relay in position G14 had failed.

It's labelled "Ignition relay-X" which isn't very descriptive, but it provides switched power to the wipers fuse, the solenoid side of the blower fan relay, the power windows and also connects to the cooling fan relay.

[gb951]

The X relay in G14 provides power to a lot of devices that are not needed when cranking (and might keep the car from having enough power to turn the engine over).

All documented in the wiring diagram.

[dr bob]

A 928 sage used to preach "relay-relay-relay" when odd electrical issues popped up. That advice is fairly universal in period Porsche cars, it turns out.

One of my pet peeves is aftermarket relays that are overrated. For a while, there was a flood of very inexpensive and proportionally reliable relays flowing from Asia. We'd search out "real" Bosch relays from Europe when we could. Alas, now even the "real" Bosch relays are made in Asia, and they are indistinguishable from the the clones/copies/forgeries without destructive disassembly. For a while I bought boxes of relays, and cut one open to inspect contacts and mechanical parts. But even that isn't enough any more, such things as silver contact plating thickness isn't measurable with my vintage M41A3 eyeballs. I still have better luck with relays from some of our known parts vendors vs. buying them on Aliexpress. But one in a bubble-pack at the local parts store could be almost anything. I just keep a bag of half a dozen in the car with 50A contact ratings, and a handy extraction tool just in case I need to do a field repair somewhere.

Meanwhile, the car has only 'stranded' me once in 30+ years and more than 100k of driving, and that was by a fuel pump relay at the bottom of my own driveway. Following that "relay-relay-relay" mantra got the car going again with less than ten minutes of diagnose-and-cure time. I still have 9 of the original 12 NOS Bosch relays I've been hoarding.

[Damo]

The X relay in G14 provides power to a lot of devices that are not needed when cranking (and might keep the car from having enough power to turn the engine over).

All documented in the wiring diagram.

I couldn’t see it in the Hayes manual. I was following all the wires for the affected components and it showed interconnects in the fuse panel, but this relay wasn’t shown. Which wiring diagram are you referring to? I need a better one than what I have.

[gb951]

944 Factory workshop manual has all the wiring diagrams for all 944 cars.